"When it is considered that this light, when obtained with mercury gas, has an efficiency at least eight times as great as that obtained by an ordinary incandescent lamp, it will be appreciated that it has its use in places where lack of red is not important, for the economy of operation will much more than compensate for the somewhat unnatural color given to illuminated objects."-- Peter Cooper Hewitt, 1902

Electrical inventor Peter Cooper Hewitt built on the mid-19th century work of German physicist
Julius Plücher
and glassblower Heinrich Geissler. By passing an electric current through a glass tube
containing tiny amounts of a gas, Plücker and Geissler found they could make light.
Although the seals leaked and soon let in too much air to allow the effect, glowing
Geissler Tubes became a scientific novelty.

While Edison and others struggled with incandescent filaments, some inventors
approached the concept of making light by using electrical discharges.
Hewitt began developing mercury-filled tubes in the late 1890s, and found that they gave off an
unappealing bluish-green light.
The amount of light, however, was startling. Hewitt realized that few people would
want his lamps in their homes, and so concentrated on developing a product for other
uses.

Photo studios made extensive use of Cooper Hewitt lamps. In an age of black and
white film, the color of a photographer's light made little difference, there just needed to
be lots of it. Industrial uses for the lamp were also many. In 1902 the Cooper Hewitt
Vapor Lamp Company (backed by the money of George Westinghouse) was established to make and market the lamps.

Ultimately, Cooper Hewitt lamps proved cumbersome to use. The necessary ballast
was heavy, and the lamps each contained as much as a pound of mercury. Development of
tungsten filament incandescent lamps in the 1910s provided almost as much efficiency
as the mercury tubes, but with a much better color. General Electric bought the Cooper
Hewitt Company in 1919, and in 1933 began marketing a new mercury vapor lamp.
Designed in Europe, this mercury lamp and the fluorescent lamps that followed, used only a fraction of the mercury Cooper Hewitt
lamps did, but
produced light much more efficiently.